Polycarbonate swelling and stretching process

ABSTRACT

PRODUCTION OF CRYSTALLINE POLYCARBONATE FILAMENTS AND FOILS BY FORMING SUCH FILAMENTS OR FOILS AND SWELLING SUCH FILAMENTS OR FOILS WITH A KETONE OR AN ESTER SWELLING AGENT, STRETCH-ORIENTING SUCH FILAMENTS OR FOILS IN THE SWOLLEN STATE   AND THEN HEAT-TREATING SUCH ORIENTED FILAMENTS OR FOILS AT A TEMPERATURE OF ABOUT BETWEEN 180 AND 260*C.

June 8, 1971 H. KUBITZEK ETAL 3584,10?

POLYCARBONATE SWELLING AND STRETCHING PROCESS Original Filed Oct. '7, 1965 F/Gl Int. Cl. 1359a 7/24 U.S. Cl. 264-288 2 Claims ABSTRACT OF THE DISCLOSURE Production of crystalline polycarbonate filaments and foils by forming such filaments or foils and swelling such filaments or foils with a ketone or an ester swelling agent, stretch-orienting such filaments or foils in the swollen state and then heat-treating such oriented filaments or foils at a temperature of about between 180 and 260 C.

This application is a streamlined continuation of ap plication Ser. No. 493,748 filed Oct. 7, 1965.

The present invention relates to a process for the manufacture of stretched, crystalline filaments and foils from amorphous or partly crystalline, unstretched filaments and foils of polycarbonates. It relates especially to filaments or cast foils from polycarbonates from 2,2-(4,4'- dihydroxydiphenyl)-propane spun dry from solutions.

In the manufacture of filaments and foils from polycarbonates, mainly from 2,2-(4,4'-dihydroxydiphenyl)- propane, structures are formed which are amorphous or only partly crystalline. However, it is well known that such filaments and foils only have useful properties if their crystallinity is sufficiently high and if they are stretched at temperatures above the glass temperature (second order transition) of polycarbonate, i.e. above 150 C.

llt has now been found that if the after-treatment of amorphous, unstretched polycarbonate filaments and foils, which is known per se, is carried out with certain liquid swelling agents, it not only produces a uniformly high crystallinity but also causes the freezing temperature (second order transition) of the polycarbonate to be lowered to such an extent, that in spite of the high crystallinity, the filaments and foils can be stretched in the swollen state without additional expenditure of heat. It is surprising that in this procedure no simple plastic deformation of the filaments and foils takes place since their mechanical properties such as tensile strength, elastic modulus, degree of elasticity and sensitivity to temperature and solvents are substantially improved by this stretching process in the swollen crystalline state. Stretching of the swollen filaments and foils is carried out at room temperature.

In carrying out the process which is described fully hereinafter, those liquid organic reagents may be used which fulfil the following conditions:

(1) They must swell the polycarbonate filaments and foils without damaging them.

(2) Their rate of ditfusion must be high.

(3) They must stimulate the swollen filaments and foils is crystallisation.

United States Patent 3,584,107 Patented June 8, 1971 (4) The crystallisation stimulated by them must proceed rapidly.

(5) The time interval between swelling and crystallisation must be small.

(6) The swelling agent must be easily removed from the filaments and foils.

These conditions are fulfilled by aliphatic ketones and esters of the general formula:

wherein R and R represent alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl or alkenyl groups such, for example as vinyl or allyl. Examples of such compounds which contain a carbonyl group are dimethylketone, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, alkyl esters of formic acid and ketones and esters.

The process is especially suitable for filaments and foils of poly- (2,2- (4,4'-dihydroxydiphenyl) propanecarbonate) which have been dry spun or cast from solution. It is also possible to use the known filmand fibre-forming polycarbonates of 2,2-(4,4'-dihydroxy-3,3-dichlorodiphenyl)- propane, of 2,2 (4,4'-dihydroxydiphenyl)-butane or mixed polycarbonates of 2,2-(4,4-dihydroxydiphenyl)-propane and 0.5 to 20- mols percent of a different dihydroxydiaryl alkane and/or a different aromatic, aliphatic or cycloaliphatic dihydroxy compound such as 4,4-dihydroxydiphenylmethane, 1,1 (4,4' dihydroxydiphenyl)-cyclohexane, 1,1(4,4'-dihydroxydiphenyl)-ethane, 4,4'-dihydroxydiphenylsulphone, 4,4-dihydroxy diphenylether, 4,4-dihydroxydiphenyl, 2,6-dihydroxynaphthalene hydroquinone, recorcinol, 1,6-hexanediol, 1,4-cyclohexanediol, p-xylyleneglycol and 2,2-(4,4-dihydroxy-ethoxydiphenyl)-propane, and lastly, mixed polycarbonates of 4,4- dihydroxy-diphenylmethane and/or other aromatic, aliphatic or cycle-aliphatic dihydroxy compounds such as those mentioned above, a wide range of proportions in the mixture being possible. The process is also suitable for filaments and foils drawn from the melt provided they are sufiiciently homogeneous.

Various methods may be employed for putting the process into practice. Thus, for example, in FIG. 1 there is shown schematically an apparatus in which continuous filament yarns having very good properties for further working up and use are produced by guiding the filaments which are in the unstretched state on the spinning spools 1 through a bath of swelling agent 2 and over a stretching mechanism 3 into a drying zone 4 and fixing zone 5. These filaments, which crystallise in the bath of swelling agent 2 and are stretched by the stretching mechanism when in the swollen state 3 in the ratio of 1:3 to 1:6, are dried and fixed and are drawn off through the preparation bath 6 and over the squeezing rollers 7.

Optimum shrinking properties are obtained in the filaments if the highest possible fixing temperature is employed, the upper limit of which is determined by melting of the crystalline components. The temperatures used are in the range of between and 260 C. The melting region of the filaments treated in this way increases towards higher temperatures with increasing stretching ratio. An increase in the fixing temperature causes a similar but less marked shift in the melting range, which is determined by the disappearance of double refraction or by the recording of DTA diagrams. With these methods of analysis, the melting point, which is characterized by the maximum on the DTA curve or by the disappearance of double refraction is found to be in the region of 240 to 260 C., depending on the stretching ratio and the fixing temperature. To ensure unhindered removal of the filaments from the spools and out of the bath of swelling agent, they are provided with a protective twist before the treatment.

Foils and spun bands of high total titres, e.g. of the kind which can be used for the manufacture of corded yarns, carpets or staple fibres, are advantageously treated as described below with reference to FIG. 2: The band or foil 1 is conveyed from the spinning spool or storage canister 2 to a roller apparatus 3 where it is conveyed through a bath of swelling agent 4 by closely positioned adjacent rollers rotating alternately in opposite directions.

The residence time in the swelling agent, i.e. in the roller apparatus, should not be less than 15 seconds. The permitted time has in practice no real upper limit. By means of the method described of transporting the band or foil, no significant tensile forces, which are due mainly to the longitudinal shrinkage on crystallisation, act on the band or foil in the region of maximum swelling, i.e. immediately before the onset of crystallisation.

Immediately on leaving the swelling and crystallisation bath 4, the swollen band or foil 1 is stretched with the aid of squeezing rollers or a stretching mechanism comprising a cascade of rollers 3 in the ratio of 1:3 to 125.5 and then runs through a drying zone 6 3 to m. in length, where 95 to 99% of the adhering and occluded swelling agent is removed with hot air at 80 to 160. This drying zone follows directly on a hot air fixing zone 7 2 to 5 m. in length in which optimum properties are imparted to the filaments or foils by the hot air at a temperature of 220 to 250 C. After leaving the fixing zone, the band passes tangentially over one or two preparation rollers 8 and then passes through rollers 9 to be deposited in canisters or wound on spools. Filaments and foils having the same properties are obtained if the stretching mechanism is not arranged behind the swelling bath, as has been described, but at the end of the whole apparatus. In both cases, the stretching process properly speaking takes place on the last roller of the crystallisation bath. This last arrangement described has technical advantages from the procedure point of view.

It is obvious that the stretching mechanism can also be arranged between the drying and fixing zone. This arrangement is especially suitable if it is desired to obtain filaments or foils with special properties by an afterstretching or by a shrinking process in the fixing zone.

The filaments and foils manufactured by the process of stretching polycarbonate filaments and foils in the swollen crystalline state are distinctly superior to those manufactured by conventional hot stretching processes. The process can be adjusted to produce a wide range of crystalline structures.

EXAMPLE 1 An 18.5% solution of polycarbonate obtained from 2,2 (4,4' dihydroxydiphenyl)-propane and phosgene in methylene chloride, having a limiting viscosity ]=0.85, was spun from a 25 aperture nozzle with an aperture diameter of 0.09 mm. into a shaft heated with slightly preheated air, drawn off over rollers and wound on to spools at a rate of 200 m./min. The unstretched endless filament yarn of a titre of 400/25 den. was rewound to impart to it a protective twist of 200/S. The spools are then placed in a bath of acetone from which the crystallised but still swollen yarn was delivered at a rate of 20 m./min to a stretching mechanism where it was stretched at a ratio of 1:4 at room temperature. The stretched yarn was then passed through a drying and fixing zone 5 m. in length, which was heated to 240 C., and fixing zone 5 m. in length, which was heated to 240 C.,

and it was then passed over rollers to be wound on to spools at a rate of m./ min. The individual filaments of the yarns treated in this manner have the following prop-' erties:

pressed as the angular measiu re of the angle of incidence (half the scatter angle) in angular degrees.

EXAMPLE 2 As in Example 1, a fibre band was spun from a 288 aperture nozzle and deposited in canisters at the rate of 180 m./min. The crude titre of the band was 4000 den. The fibre bands were conveyed to a roller apparatus 10 m. in length, which was filled with acetone (see FIG. 2), where the bands were conveyed through the acetone bath at a rate of 5 m./min. by rollers rotating alternately in the one or other direction. The diameter of the rollers was 8 cm., the distance between the rollers 0.5 cm. The rollers were immersed to a depth of 2 cm. in the acetone. At a distance of 40 cm. behind the last roller was a stretching mechanism which stretched the crystalline, swollen filaments in the ratio of 123.75 at room temperature. In an adjacent hot :air drying zone 3 m. in length, which was at a temperature of C., the stretched fibre band was dried before it was drawn directly through the fixing zone which was 2.5 m. in length and at a temperature of 240 C., and after the application of a suitable preparation, the band was either wound on to spools or again deposited in canisters. The individual filaments of the band treated in this way were found to have the following properties:

Titre: 3.9 den.

Strength: 4.0 g./den.

Elongation at break: 44%

Modulus of elasticity at 1%: 380 kg./mm. Shrinkage on boiling (10 minutes in boiling water): 0.1% Thermoshrinkage (0.5 hour at C.): 0.3% Relative loop strength: 70%

Relative loop elongation: 58%

X-ray interference width 1.05

Degree of elasticity at 8% elongation: 100% Shrinking in perchloroethylene: 0.1%

1 See footnote 1 in Example 1.

EXAMPLE 3 After the treatment in acetone, the fibre band spun as in Example 2 was drawn by the stretching mechanism, which was now arranged behind the fixing zone, through the drying and fixing zone, no gap being left between the roller apparatus and the drying zone or between the drying zone and the fixing zone. Under the conditions of Example 2, the individual filaments were found to have the same properties.

EXAMPLE 4 Using the arrangement of Example 3, the bands spun according to Example 2 were stretched in the ratio of 1:5.1. The individual filaments then had the following properties:

Titre: 2.8 den.

Strength: 5.1 g./den.

Elongation at break: 25%

Modulus of elasticity at 1% 490 kg./mm. Shrinkage on boiling mins. in boiling water) 0.6% Thermoshrinkage (0.5 hour at 150 C.) 1.5% Relative 100p strength: 35%

Relative loop elongation: 26%

X-ray interference width 1.1

Degree of elasticity at 8 elongation: 100% Shrinkage in perchloroethylene: 0.25%

See footnote 1 in Example 1.

EXAMPLE 5 In accordance with Example 3, the fibre band was treated in the roller apparatus with ethyl acetate. The properties of the individual filaments corresponded to those in Example 2.

EXAMPLE 6 A polycarbonate foil of 2,2-(4,4-dihydroxydiphenyl)- propane cast from methylene chloride solution and 60p. in thickness was drawn through acetone in a roller apparatus at a speed of 5 m./min., stretched with a suitable stretching mechanism in the ratio of 1:3.5 at room temperature, and then dried and fixed by heat. The resulting film had a strength of 31 kg./-rnrn. and an X-ray interference Width of 1.1.

What is claimed is:

1. Process for the manufacture of crystalline polycarbonate filaments or foils from at least partially amorphous polycarbonate materials from a monomer selected from the group consisting of 2,2-(4,4'-dihydroxydiphenyl) propane carbonate, 2,2-(4,4'-dihydroxy-3,3'-dichlorodiphenyl)propa-ne carbonate and 2,2-(4,4'-dihydroxydiphenyl)- butane carbonate or mixtures thereof with at least one member selected from the group consisting of 4,4'-dihydroxydiphenyl methane, l,l-(4,4'-dihydroxydiphenyl)cyclohexane, 1,1-(4,4'-dihydroxydiphenyl) ethane, 4,4'-dihydroxydiphenyl sulphone, 4,4-dihydroxydiphenylether, 4,4'-dihydroxydiphenyl, 2,6-dihydroxynaphthalene, hydroquinone, resorcinol, 1,6-hexanediol, 1,4-cyclohexanediol, p-xylyleneglycol, and 2,2-(4,4'-dihydroxy-ethoxydiphenyl)propane, which process comprises treating said filaments or foils with a swelling agent of a general formula selected from the group consisting of E II t R R and RCOR wherein R and R each are selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, and tertbutyl; stretching said swollen filaments or foils at a stretch ratio of about 1:3 to 1:6 at room temperature; drying said filaments or foils; and then subjecting the dried and stretched filaments or foils to heat treatment at the highest possible fixing temperature up to the melting point of the polycarbonate polymer of said filaments or foils between about and 260 C.

2. Process as claimed in claim 1 wherein R and R are the same.

References Cited FOREIGN PATENTS 138,328 8/1950 Australia 264-210 634,001 4/1963 Belgium 264210 902,580 8/ 1962 Great Britain 264--2l0 1,377,671 9/1964 France 264210 JULIUS FROME, Primary Examiner H. MINTZ, Assistant Examiner U.S. C1. X.R.

HARRY L ZEFSL.LFEUElQELEAQQ.-PELANVQEeQLKALm Inventor (.FJ

ahmwidentified pnLont It is; mnrtifiud that error ap ears; in L110 as shown be] cm:

and LhuL said Lcuurs; l'uLe-nt are hereby corrected f Column 3, lines "lb-75, after "240 C. c lelete "and fixing "I zone 5 m. in length, which was heated to 240 C.

Signed and sealed this 26th day of October 1971.

(SEAL) Attest:

EDWARD M.FLE'ICHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

